Adjustable flex backpack frame

ABSTRACT

A backpack including an adjustable frame including at least one reinforcement stay having a first side, a second side opposite the first side, and a longitudinal axis, wherein the reinforcement stay includes an asymmetrical flex material configured such that a flexural modulus of the reinforcement stay in a first direction, in which the reinforcement stay flexes about the longitudinal axis such that the first side becomes concave, is greater than a flexural modulus in a second opposing direction, in which the reinforcement stay flexes about the longitudinal axis such that the second side becomes concave, wherein the backpack is configured such that the reinforcement stay can be selectively oriented in either a first orientation, in which the first side of the reinforcement stay faces toward a wearer of the backpack, or a second orientation, in which the second side of the reinforcement stay faces toward the wearer of the backpack.

FIELD OF DISCLOSURE

The present disclosure relates to backpacks, specifically, backpacks with adjustable flexible frames.

BACKGROUND OF THE DISCLOSURE

Currently, backpackers often suffer from not having a flexible, adjustable backpack frame with a stiffness that can be matched to the changing mass of the backpacker's load over the course of use. It is common for hunters in particular to begin a hike with a light load and then need to carry out very heavy loads after a successful hunt to transport meat and game. It would be advantageous in these situations to have a backpack that is adjustable between flexible and rigid frames for load hauling purposes. Thus, there is a need for an adjustable backpack with a frame that is capable of changing between flexible and rigid structures in a simple manner that is quick and easy to implement, while minimizing extra parts.

SUMMARY OF THE DISCLOSURE

The terms “disclosure,” “the disclosure,” “this disclosure” and “the present disclosure,” as used in this document, are intended to refer broadly to all of the subject matter described herein or to limit the meaning of the scope of the patent claims below. This summary is a high-level overview of various aspects of the disclosure and introduces some of the concepts that are further detailed in the Detailed Description section below. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used in isolation to determine the scope of the claimed subject matter. The subject matter should be understood by reference to appropriate portions of the entire specification, any or all drawings, and each claim.

Embodiments of the present disclosure relate to a backpack including an adjustable frame including at least one reinforcement stay having a first side, a second side opposite the first side, and a longitudinal axis, wherein the reinforcement stay includes an asymmetrical flex material configured such that a flexural modulus of the reinforcement stay in a first direction, in which the reinforcement stay flexes about the longitudinal axis such that the first side becomes concave, is greater than a flexural modulus in a second opposing direction, in which the reinforcement stay flexes about the longitudinal axis such that the second side becomes concave, wherein the backpack is configured such that the reinforcement stay can be selectively oriented in either a first orientation, in which the first side of the reinforcement stay faces toward a wearer of the backpack, or a second orientation, in which the second side of the reinforcement stay faces toward the wearer of the backpack

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a further understanding of the disclosure and are incorporated in and constitute a part of this specification, illustrate embodiments, and together with the description serve to explain the principles of the present disclosure;

FIG. 1 is a perspective view of a backpack, in accordance with embodiments described herein;

FIG. 2 is a perspective view of a stay of a backpack, in accordance with embodiments described herein;

FIG. 3 is a view of the stay of FIG. 2 flexing in a relatively flexible direction, in accordance with embodiments described herein;

FIG. 4 is a view of the stay of FIG. 2 flexing in a relatively stiff direction, in accordance with embodiments described herein;

FIG. 5 is a perspective view of a stay being rotated about a longitudinal axis thereof, in accordance with embodiments described herein;

FIG. 6 is a perspective view of a first configuration of two stays, in accordance with embodiments described herein;

FIG. 7 is a perspective view of a second configuration of two stays, in accordance with embodiments described herein;

FIG. 8 is a perspective view of a third configuration of two stays, in accordance with embodiments described herein;

FIG. 9 is an example of an external frame for a backpack including the reinforcement stays; in accordance with embodiments herein;

FIG. 10 is an example of an external frame for a backpack including the reinforcement stays; in accordance with embodiments herein; and

FIG. 11 is an example of another external frame for a backpack including the reinforcement stays; in accordance with embodiments herein;

FIGS. 12A-D are examples of a portion of a backpack showing the reinforcement stays in a first (FIG. 12A), a second (FIG. 12B), a third (FIG. 12C) and a fourth (FIG. 12D) orientation.

DETAILED DESCRIPTION

Persons skilled in the art will readily appreciate that various aspects of the present disclosure can be realized by any number of methods and apparatus configured to perform the intended function. It should also be noted that the description of illustrative embodiments according to principles of the present disclosure is intended to be read in connection with the accompanying drawings, which are to be considered part of the entire written description. In the description of embodiments disclosed herein, any reference to direction or orientation is merely intended for convenience of description and is not intended in any way to limit the scope of the present disclosure.

For purposes of this disclosure, the phrase “adjustable flex” is used to describe a material (or stay) that provides asymmetric flexural (flex) modulus, meaning that the material has two different flex moduli when the material is flexed in opposing directions. For example, that adjustable flex material has a relatively lower flex modulus, i.e., the reinforcement stay 124 is relatively flexible when flexed or bent in a first direction as shown in FIG. 3, the first direction indicated by arrows D1. However, the adjustable flex material has a relatively higher flex modulus, i.e., the reinforcement stay 124 is relatively stiff when flexed or bent in a second direction opposing the first direction as shown in FIG. 4, flexing in the direction indicated by arrows D2. Also, “adjustable flex material” as used herein refers to a material that can be subjected to repeated bending and release cycles at 50% of the force required to break the material without breaking, cracking or permanently deforming the material. In some embodiments, the material can be flexed at 50% of the force required to break the material for 100 flex and release cycles. In other embodiments, the material can be flexed at up to 50% of the force required to break the material for 1,000 flex and release cycles without breaking, cracking or permanently deforming the material; in still further embodiments, the material can be flexed at up to 50% of the force required to break the material for 5,000 flex and release cycles without breaking, cracking or permanently deforming the material.

The present disclosure relates to a backpack including an adjustable frame including at least one reinforcement stay having a first side, a second side opposite the first side and a longitudinal axis, wherein the at least one reinforcement stay comprises an asymmetrical flex material configured such that a flexural modulus of the at least one reinforcement stay in a first direction, in which the at least one reinforcement stay flexes about the longitudinal axis such that the first side becomes concave, is greater than a flexural modulus of the at least one reinforcement stay in a second direction, in which the at least one reinforcement stay flexes about the longitudinal axis such that the second side becomes concave, and wherein the second direction is opposite the first direction, wherein the backpack is configured such that the at least one reinforcement stay can be selectively oriented in either a first orientation or a second orientation, wherein in the first orientation, the first side of the at least one reinforcement stay faces toward a wearer of the backpack, and wherein, in a second orientation, the second side of the at least one reinforcement stay faces toward the wearer of the backpack.

The present disclosure utilizes one or more reinforcement stays, for example, one or more reinforcement stays that are an asymmetrically flexible material in a backpack in order to provide greater stiffness in one direction of bending versus an opposite direction of bending. In general, a backpack that conforms, at least partially, to a wearer's back when the wearer is bending forward at the waist—i.e., when the wearer is curving his or her back with a lighter load—is desirable. However, as the wearer transitions to carrying a heavy load, a more rigid frame that better supports the increased mass is desirable. This transition from flexible to rigid can be achieved by using one or more reinforcement stays that are made with an asymmetrically flexible material. The reinforcement stays are removable from a holding area, such as a pocket in the backpack or another attachment/detachment mechanism, and can be flipped prior to reinsertion into the holding area. This flipping of the reinforcement stays results in an increased stiffness when trying to flex inwardly toward the wearer's back, and thus, a more rigid frame for hauling heavier loads.

The present disclosure provides several advantages over the prior art. Conventional backpacks have relatively solid frames formed of, for example, aluminum or carbon fiber. These frames are often one-piece designs where the elements are welded together to form a rigid frame. In contrast, the backpack of the present disclosure allows the user to tailor the backpack to his or her needs, resulting in a dynamic and more comfortable user experience. Furthermore, the frame of the present disclosure may be composed of several removable parts so that multiple levels of flexibility may be achieved through various selective orientations of the components, as will be described in further detail below.

As described herein, a backpack is provided with an adjustable frame including at least one reinforcement stay including an asymmetrically flexible material (flex material). In particular, the asymmetric flex material is asymmetrically flexible relative to a longitudinal bending plane. For example, a flexural modulus of the asymmetric flex material in a positive bending direction is different from a flexural modulus of the asymmetric flex material in a negative bending direction while in the same longitudinal orientation. In some embodiments, a backpack frame is a part of the backpack and the frame comprises the reinforcement stay and optionally one or more frame elements that hold the reinforcement stay. The reinforcement stay may be rotated 180 degrees about a longitudinal or horizontal axis thereof to change the flexibility of the frame, depending on the load to be carried. In some embodiments, the asymmetric flex materials increase the stiffness of the frame by a factor of 2:1, 5:1 or higher.

With reference to FIG. 1, the backpack 100 includes a bag portion 102 having approximately a parallelepiped shape that defines an inner compartment (not shown) that is accessed through an opening 106. The bag portion 102 has a body-contacting or back side 108, a non-body contacting or front side 110, left and right side panels 112, 114, respectively, a top 116, a bottom 118 and shoulder straps 119.

In some embodiments, the backpack 100 includes a backpack frame, which may be an internal frame (FIG. 1) or an external frame (FIGS. 12A-12D). The backpack frame may include one or more frame elements 122 that are configured to hold the one or more reinforcement stays 124. The frame may be an external frame, wherein the reinforcement stays 124 are a portion of the frame, and the bag portion 102, shoulder straps and/or waist belt can be attached directly to the frame. The frame may be an internal frame design, wherein a pocket or holding area 126 is designed to receive the frame and/or the reinforcement stays 124. The backpack may also be a frameless backpack, wherein the one or more reinforcement stays 124 are inserted into one or more holding areas 126 in the backpack 100, the holding areas being shaped to approximately the same shape as the reinforcement stays 124, without the use of additional frame elements. As an example of an internal frame, FIG. 1 shows a frame that is composed of two reinforcement stays 124 and two frame elements 122 that are configured to hold the reinforcement stays 124 in a fixed position relative to each other, while still allowing the reinforcement stays 124 to flex. It is noted that, although the frame of FIG. 1 depicts two vertically oriented reinforcement stays, any of the disclosed frames may include one, two, three or any number of vertically or horizontally oriented reinforcement stays in any arrangement, depending on the type of backpack or intended purpose of the backpack. In some embodiments, the reinforcement stays 124 are housed within a holding area 126. The holding area 126 may be a slot, a pocket or some other compartment that is able to accommodate the frame, the reinforcement stays 124 or both, as depicted in FIG. 1. In some embodiments, the backpack 100 may include one or more holding areas 126 that are positioned substantially parallel to one another. In other embodiments, the holding areas 126 are in a stacked configuration. In other embodiments the backpack includes one long holding area 126 that is sized to hold one or more reinforcement stays 124 in a stacked arrangement, as will be described in further detail below. The holding areas 126 optionally include a closure, such as, for example, a zipper, a button, a hook and loop fastener or any other closure, to prevent the reinforcement stays 124 from falling out of the holding areas 126. In general, the holding area 126 should be sized so that the reinforcement stays 124 and/or the frame including the one or more reinforcement stays 124 are held relatively fixed, so that the frame and/or the reinforcement stays 124 do not move within the holding area 126, see FIG. 12A-12D, which show a part of the bag portion 102. FIGS. 12B-12D also show individual reinforcement stays 124, including the holding areas 126 with reinforcement stays 124 inserted so that one side of the reinforcement stays 124 are oriented within the holding areas so that the A side of both reinforcement stays 124 are oriented in a first direction (FIG. 12B), the removal of the reinforcement stays 124 from the holding areas 126 (FIG. 12C) and the reinsertion of the reinforcement stays 124 with the A side oriented in the opposite direction from the first direction (FIG. 12D).

The reinforcement stays 124 may take any of a plurality of sizes and shapes. In some embodiments, as depicted in FIG. 2, the reinforcement stays 124 are elongated planar elements, having both a length and width that is greater than the thickness (e.g., into the page). In other embodiments, however, the reinforcement stays 124 may be planar elements or panels that conform to the shape of the holding area 126. In some embodiments, the reinforcement stays 124 may be flat elements or pre-shaped elements that match or conform to the wearer's back profile or a generalized back profile. In some embodiments, the reinforcement stays 124 are changeable from a flat shape to a shape that conforms to the wearer's back profile or a generalized back profile.

As described above, the reinforcement stays 124 comprise an adjustable flex material that, when the reinforcement stays 124 are in a bending orientation, has a flexural modulus in a first bending direction that is different from a flexural modulus in a second opposing bending direction. In some embodiments, the reinforcement stays 124 comprise a flex material that is relatively flexible in one direction and relatively stiff in an opposing direction. In some embodiments, the asymmetric flex material has an asymmetrically stiff material performance in longitudinal bending—i.e., bending about a longitudinal axis of the asymmetric flex material. For example, looking to FIG. 2, a longitudinal-shaped reinforcement stay 124 is depicted. The reinforcement stay 124 has a first longitudinal side A, and a second opposing longitudinal side B. As can be seen in FIGS. 3-4, when the reinforcement stay 124 is flexed about its longitudinal axis L toward side A (i.e., such that side A becomes concave), or in a relatively flexible direction D1 (depicted in FIG. 3), the reinforcement stay 124 has a higher flexural modulus than when the reinforcement stay 124 is flexed about its longitudinal axis L toward side B (i.e., such that side B becomes concave), or in a relatively stiff direction D2 (depicted in FIG. 4). In this embodiment, side A is a relatively flexible side and side B is a relatively stiff side. In some embodiments, the flex modulus of the reinforcement stay 124 in the relatively flexible direction D1 relative to the stiff direction D2 is in the range of from 1.5:1 to 6:1. In other embodiments, the ratio of the flex modulus of the reinforcement stay 124 in the relatively flexible direction D1 relative to the flex modulus of the reinforcement stay 124 in the stiff direction D2 is in the range of from 1.5:1 to 5:1. In other embodiments, the ratio of the flex modulus of the reinforcement stay 124 in the relatively flexible direction D1 relative to the flex modulus of the reinforcement stay 124 in the relatively stiff direction D2 is in the range of from 1.5:1 to 4:1. In other embodiments, the ratio of the flex modulus of the reinforcement stay 124 in the relatively flexible direction D1 relative to the flex modulus of the stay 124 in the relatively stiff direction D2 is in the range of from 1.5:1 to 3:1. In other embodiments, the ratio of the flex modulus of the reinforcement stay 124 in the relatively flexible direction D1 relative to the flex modulus of the reinforcement stay 124 in the relatively stiff direction D2 is in the range of from 2:1 to 6:1. In other embodiments, the ratio of the flexibility of the reinforcement stay 124 in the relatively flexible direction D1 relative to the flexibility of the reinforcement stay 124 in the relatively stiff direction D2 is greater than 2:1. In still further embodiments, the ratio of the flexibility of the reinforcement stay 124 in the relatively flexible direction D1 relative to the flexibility of the reinforcement stay 124 in the relatively stiff direction D2 is less than 6:1.

Although FIGS. 2-4 show a reinforcement stay that has different flexibilities about a longitudinal axis, the difference in flexibility of the stay may be relative to other axes thereof. For example, in some embodiments, the reinforcement stay may have different bending flexibilities in opposing directions about a horizontal axis thereof.

In some embodiments, the asymmetric flex material comprises a carbon fiber material with flexible properties. In some embodiments, the asymmetric flex material comprises the material sold as CARBITEX AFX®.

In some embodiments, the flexibility of the backpack 100 is changed by the flipping of the frame elements 122 and/or reinforcement stay 124. Specifically, as depicted in FIG. 5, a reinforcement stay 124 can be rotated 180 degrees about its longitudinal axis L such that the first and second bending directions are flipped. For example, if the relatively flexible-bend side A of the reinforcement stay 124 is initially facing the wearer's back, rotation of the reinforcement stay 124 180 degrees about the longitudinal axis L of the reinforcement stay 124 results in the relatively stiff-bend side B of the reinforcement stay 124 facing the wearer's back. It is noted that changing the flexibility of the reinforcement stays 124 does not occur by simple rotation of the reinforcement stays 124 90 degrees to change the orientation of the reinforcement stays 124 from a longitudinal to a transverse direction. Rather, the variance in flexibility occurs when the asymmetric flex material has a different flex behavior in opposing bending directions in the same longitudinal orientation.

In some embodiments, multiple reinforcement stays 124 are arranged in a stacked configuration so that the flexibility of the backpack 100 is tunable to the wearer's preference. For example, in some embodiments, two reinforcement stays 124 including adjustable flex materials are longitudinally stacked, as depicted in FIGS. 6-8. In these embodiments, the reinforcement stays 124 could be oriented to provide three different levels of flex. For example, in one configuration both reinforcement stays 124 may be oriented with their relatively stiff-bend sides B facing the wearer's back, providing the a first level of flex modulus to the backpack 100, as depicted in FIG. 6. In a second configuration, both reinforcement stays 124 may be oriented with their relatively flexible sides A facing the wearer's back 10, providing a second level of flex modulus to the backpack 100, as depicted in FIG. 7. In a third configuration, one reinforcement stay 124 is oriented with the relatively stiff-bend side B facing the wearer's back 10 and the second reinforcement stay 124 is oriented with the relatively flexible side A facing the wearer's back 10, as depicted in FIG. 8. This configuration would provide a third level of flex modulus to the backpack 100 that is in between the first and second flex moduli. Thus, three different levels or degrees of flex may be imparted to the backpack 100, depending on the size of the load and the wearer's preference, when using two reinforcement stays 124 in a stacked configuration.

In some embodiments, the backpack 100 does not include a holding area 126 wherein the reinforcement stays fit, but rather, the reinforcement stays 124 are attached to an external frame 130. FIGS. 9-11 show examples of external frames 130 including the reinforcement stays 124, frame element 132 and optional waist belt 136. Waist belt 136 of FIG. 10 can further include pockets 134 wherein the reinforcement stays 124 can be inserted to stabilize the position of the reinforcement stays 124. While FIGS. 9 and 10 show the frame element 132 to be about the same height as the reinforcement stays 124, the stays can be shorter or longer than the frame element 132 in order to provide more or less flexibility to the backpack frame. FIG. 11 shows an example where the reinforcement stays 124 are longer than frame element 132. Frame 130 can optionally comprise reinforcement stay element 138 which stabilizes the ends of the reinforcement stays 124 within the frame 130 and the waist belt 136. Optional stabilizer element 142 can be present to help stabilize the position of the reinforcement stays 124, especially when using relatively longer reinforcement stays 124. Typically, external frames have one or more attachment points so that items like shoulder straps 140, load stabilizers 144, straps/releasable fasteners 146 and bag portions (not shown) can be attached to the frame 130. In these embodiments, the reinforcement stays 124 could be friction fit within the frame elements 132 and/or the waist belt 136. As was mentioned previously, while the figures show two rectangular shaped reinforcement stays 124, other rectangular or non-rectangular shapes could be used, as well as two or more reinforcement stays 124 in stacked configuration. In those embodiments where multiple reinforcement stays 124 are used, each individual reinforcement stay 124 can independently have its own shape, which may or may not be the same as the other reinforcement stays 124. In some embodiments, the reinforcement stays 124 include clamps or other known means to hold the reinforcement stays 124 relative to one another and to the backpack 100 to form a backpack frame. Alternative securing methods for the reinforcement stays 124 could be used, for example, clips, buttons, tabs, slots or a combination thereof. In some embodiments, the reinforcement stays 124 may be removable from the frame element 132 or from the backpack 100 and adjustable depending on the amount of flex required. That is, upon removal, the reinforcement stays 124 may be flipped or rotated about longitudinal axis and reinserted into the frame element 132 or the backpack 100 to change the flex from relatively flexible to relatively stiff or vice versa.

In some embodiments, the backpack 100 has a frame sheet that fits across the back of the backpack 100 and protects the wearer from being poked by items within the backpack 100 when the backpack 100 is being worn. In some embodiments, the frame sheet comprises the asymmetric flex material, providing the backpack 100 with the adjustable flex properties.

In some embodiments, the backpack 100 is a “no frame” backpack. Rather, in some embodiments, for example, the backpack of FIG. 1, the backpack 100 includes one or more holding areas 126 within the bag portion 102, each holding area 126 being configured to hold a reinforcement stay 124, without a frame element 122. In other embodiments, the holding areas 126 may be positioned on the outside of the backpack 100. The removable reinforcement stays 124 are positioned within the holding areas 126 to increase the stiffness of the backpack 100 as desired. The holding areas 126 optionally include a closure, such as, for example, a zipper, a button, or any other closure, to prevent the reinforcement stays 124 from falling out of the holding areas 126. In these embodiments, the reinforcement stays 124 are removable from the backpack 100 and adjustable depending on the amount of flex required. That is, upon removal, the reinforcement stays 124 may be flipped or rotated about their longitudinal axis and reinserted into the backpack 100 to change the flex from relatively flexible to relatively stiff or vice versa.

Although the foregoing discussion relates to flexible materials incorporated into backpacks, the present disclosure may be incorporated into a variety of different articles such as, for example, footwear, gloves, garments, etc., where it may be desirable to have flexibility in one direction and limited flexibility in the opposite direction.

The foregoing discussion has been presented for purposes of illustration and description. Further, the description is not intended to limit the disclosure to the form disclosed herein. Consequently, variation, modification and combination commensurate with the above teachings, within the skill and knowledge of the relevant art, are within the scope of the present disclosure. The embodiments described herein and above are further intended to explain the best mode presently known and to enable other skilled in the art to utilize the embodiments, as such, or in other embodiments, and with the various modifications required by their particular application or uses of the embodiments. It should be further construed that all of the embodiments disclosed herein may be presented individually or in combination to create embodiments that should be deemed within the scope and teaching of the specification presented herein. It is intended that the appended claims be construed to include alternative embodiments to the extent permitted by the prior art. 

What is claimed is:
 1. A backpack, comprising: an adjustable frame comprising at least one reinforcement stay having a first side, a second side opposite the first side, and a longitudinal axis, wherein the at least one reinforcement stay comprises an asymmetrical flex material configured such that a flexural modulus of the at least one reinforcement stay in a first direction, in which the at least one reinforcement stay flexes about the longitudinal axis such that the first side becomes concave, is greater than a flexural modulus of the at least one reinforcement stay in a second direction, in which the at least one reinforcement stay flexes about the longitudinal axis such that the second side becomes concave, and wherein the second direction is opposite the first direction, wherein the backpack is configured such that the at least one reinforcement stay can be selectively oriented in either a first orientation or a second orientation, wherein, in the first orientation, the first side of the at least one reinforcement stay faces toward a wearer of the backpack, and wherein, in the second orientation, the second side of the at least one reinforcement stay faces toward the wearer of the backpack.
 2. The backpack of claim 1, wherein the asymmetrical flex material is configured to increase a stiffness of the adjustable frame by a factor of from 2:1 to 5:1.
 3. The backpack of claim 1, wherein the asymmetrical flex material is configured to be subjected to repeated bending and release cycles at 50% of a force required to break the asymmetrical flex material without breaking the asymmetrical flex material.
 4. The backpack of claim 1, wherein the asymmetrical flex material is configured to be subjected to repeated bending and release cycles at 50% of a force required to break the asymmetrical flex material without breaking the asymmetrical flex material for up to 5,000 flex and release cycles.
 5. The backpack of claim 1, wherein the adjustable frame comprises a plurality of reinforcement stays.
 6. The backpack of claim 1, wherein the adjustable frame is an external frame.
 7. The backpack of claim 1, wherein the adjustable frame is an internal frame.
 8. The backpack of claim 1, wherein the flexural modulus of the at least one reinforcement stay in the first direction relative to the second direction is from 1.5:1 to 6:1.
 9. A backpack, comprising: at least one reinforcement stay having a first side, a second side opposite the first side, and a longitudinal axis, wherein the at least one reinforcement stay comprises an asymmetrical flex material configured such that a flexural modulus of the at least one reinforcement stay in a first direction, in which the at least one reinforcement stay flexes about the longitudinal axis such that the first side becomes concave, is greater than a flexural modulus of the at least one reinforcement stay in a second direction, in which the at least one reinforcement stay flexes about the longitudinal axis such that the second side becomes concave, and wherein the second direction is opposite the first direction, wherein the backpack is configured such that the at least one reinforcement stay can be selectively oriented in either a first orientation or a second orientation, wherein, in the first orientation, the first side of the at least one reinforcement stay faces toward a wearer of the backpack, and wherein, in the second orientation, the second side of the at least one reinforcement stay faces toward the wearer of the backpack.
 10. The backpack of claim 9, wherein the asymmetrical flex material is configured to increase a stiffness of the backpack by a factor of from 2:1 to 5:1.
 11. The backpack of claim 9, wherein the asymmetrical flex material is configured to be subjected to repeated bending and release cycles at 50% of a force required to break the asymmetrical flex material without breaking the asymmetrical flex material.
 12. The backpack of claim 9, wherein the asymmetrical flex material is configured to be subjected to repeated bending and release cycles at 50% of a force required to break the asymmetrical flex material without breaking the asymmetrical flex material for up to 5,000 flex and release cycles.
 13. The backpack of claim 9, comprising a plurality of reinforcement stays.
 14. The backpack of claim 9, wherein the flexural modulus of the at least one reinforcement stay in the first direction relative to the second direction is from 1.5:1 to 6:1. 